1. Field of the Invention
The invention relates to a floor-mounted (or pushdown) forging press of the kind having a static piston on the top beam of the press and a cylinder which slides on the piston for the forging stroke and acts as a toolholder, as well as a coaxial bore for supplying pressure medium to the moving cylinder, which bore extends through the top beam and the piston.
2. Description of the Prior Art
Multi-cylinder and single-cylinder forging presses are known wherein eccentric forces occur which may cause lateral movements or skewing of the toolholder, for example of the travelling, beam or cross-head of the press. In an arrangement comprising a stationary cylinder and a movable piston, for enabling these forces to be better absorbed, the piston forces are transmitted to the tool-holder through ball cups and a bearing shoe between them. The faces of the bearing shoe, machined to a barrelled shape, permit lateral movements as well as skewing of the travelling cross-head of the press. In this arrangement, at least two pistons are present in the forging press. In the classical example, a guide ram effects the central guiding of the travelling cross-head. This guide ram is known as a "Davy pin". The pistons move in stationary cylinders. The pressure medium is supplied at the cylinder side, so that the operative face of the piston can be closed off. (See Ernst Muller, "Hydralische Pressen und Druckflussigkeitsanlagen", Vol. 1: "Schmiedepressen", 3rd. edition, Springer-Verlag, Berlin/Gottingen/Heidelberg, 1962, pp 32-34 and 48-64, in particular page 59 and FIGS. 50 and 51 on page 63).
A disadvantage of the known arrangements is that with the use of ball cups and a bearing shoe for force-transmission, the press cylinder must always be designed to be stationary, so as to ensure supply of pressure medium.
Also known are single-cylinder presses wherein the cylinder executes the stroke movement, whereas the piston is stationary. The cylinder is also guided externally. The piston, firmly inserted in the top beam on the press, must of necessity participate in the guiding action if the machine is set in the ideal manner. From the design point of view, this means that the guides are excessively complicated, and in practice perfect operation can be achieved only if the outer guide of the cylinder is optimally adjusted. In practice, particularly in forging operations, it is very doubtful whether such optimal setting can be achieved with the existing means.